Bachmann Co1 Bogies: Subframes

This section describes the construction of the bogie subframes, taking one at a time.

Components and features of bogie subframe

Subframe mainframes Check that the vertical slots in the sides of the Subframe Mainframe etches (S4) are clear to take the etch thickness.

Scrap etch slot gauge/opening tool Part of the etched fret from around the mainframe's axle slots makes a suitable tool, when held in a hand vice, for checking and, if necessary, reaming the slots to pass the material thickness.

Folded mainframe Make the two main longitudinal folds in each Mainframe. Each fold is in three parts carried over the cross members under each axle slot.

Ensure the folds are at a true right angle throughout.

Inner Seats Remove the Inner Seat etches (S12) from the fret. Check that the slot in each one is clear to take the material thickness.

Folding inner primary seat Fold out the spring seat on each etch…

Folding support laminate on inner seat etch …and then fold back the 180° folds at the other end of each etch, with the half-etched folding tags on the insides of the folds.

Inner ear etches Remove the Inner Ear etches (S1) from the fret.

Folded Inner Ear etch Fold out the inner lateral and longitudinal restraint ears.

Inner Ear on assembly support Arrange a supporting surface which will fit inside the width of the Mainframe, and place one of the Inner Ear etches on the surface.

The baseplate of your etch will have two chamfered corners: orientate it so that they are facing away from the edge of the supporting jig.

Inner Ear and Seat etches assembled Select the two Inner Seat (S12) etches whose slots match the ears of the Inner Ear etch, and fit them over the ears.

Feeding Inner Ears and Seats through mainframe Examine the slots in the Mainframe etch to determine which side matches the Seat and Ear components, and feed the ears and seats through the slots in the Mainframe.

Take time to align each folded part with its slot, and ease them through carefully but firmly.

Inner Seats and Ears in position Apply flux to the laminations - the etched holes facilitate this - and hold them firmly together while soldering them in. Ensure that the half-etched recess, and the slots for the springs remain free of solder.

Apply a fair-sized globule of solder to the edge of the laminations, keeping the iron in contact until the solder runs off it and flashes through the joint.

Repeat for the Inner Ear and Inner Seat etches on the other side of the Mainframe.

Remove the Outer Ear (S2), Secondary Seat (S13) and Secondary Seat Spacer (S14) etches from the fret.

Outer Ears and Secondary Seats folded Fold out the ears and seats.

Outer Ear etch on the assembly jig Place one of the Outer Ear etches on the support jig, with its longest edge facing away from the end of the jig.

Outer Ear etch in Mainframe Examine the slots in the Mainframe etch to determine which side matches the Outer Ear etch, and insert the ears and seat through the slots in the Mainframe.

Secondary Seat etches Take the pair of Secondary Seats for that side and place them on the jig. Place another block on the jig to act as a fence.

Secondary Spacer Fit one of the Spacers over the Seat etches, applying flux to all adjacent surfaces.

Outer Ears and Secondary Seat Place the Mainframe over the secondary seat assembly. Apply flux to all surfaces and hold the laminations firmly together, pushing it up against the fence to ensure the Secondary Seat etches are fully home in their slot. Check that the bottom edges of the components are aligned with the bottom edge of the Mainframe, and solder up the assembly.

Repeat for the Outer Ears and Secondary Seat on the other side of the Mainframe.

Axle and Lower Axle etches Remove the Pony Axle (S5) and Pony Lower Axle (S8) etches from the fret.

Check that the main bodies of the wheel bearings will pass through the holes in the Axle and between the legs of the Lower Axle, filing the etches as required.

Axle and Lower Axle folded Fold up the Axle and Lower Axle etches.

Bearings fitted to axle etch Remove any burrs from the bearings, and check that the 2mm axle is a running fit, opening them out further with a broach if necessary.

Using the 2mm axle to align the bearings, insert them through the holes in the Axle etch.

Lower Axle etch in place Slide the Lower Axle etch into place over the bearing bodies to the point where its vertical upstands are in contact with the lower face of the Axle etch.

On the production etches, the central upstand has a tab which engages in a slot in the edge of the Axle etch.

Pony assembly You can turn down the ends of a pin-point axle to represent the cylindrical extensions of the prototype's carrying axles.

Pony assembly in soldering jig Holding one of the bearings firmly against the outer edge of the Axle etch, and ensuring that the two etches are correctly fitted together, apply flux to the area around the bearing and apply a generous amount of solder to the joints, keeping the iron in place until the solder flashes around the joint.

Repeat for the other bearing.

Pony Frame etch Remove the Pony Frame etch (S7) from the fret.

Folding horncheeks Fold back the horncheeks of the Pony Frame beyond a right angle to approximately 70° from the side of the frame.

Frame return folds Fold the frame returns to 90°.

Folded horncheeks and returns Completed horncheek and return folds.

Folding frame sides Fold up the two sides of the frame.

Folded Pony Frame etch Completed Pony Frame etch.

Matching horncheeks to pony axle curvature Offer up the pony axle assembly to the frame, and adjust the horncheek folds to match the curvature of the edges of the pony axle etches.

Provide firm support for the sides of the frame when adjusting the folds, to avoid distorting them.

Pony Flitching etch Remove the Pony Flitching etch (S10) from the fret.

Check that the 8 thou spring wire will pass the hole in the etch. Drill it through 0.3mm if necessary.

Control spring seat fold Fold up the seat for the pony truck's control spring…

Pony control spring clip …and fold over the retaining clip (it's been extended a bit on the production etch).

Reinforce the two seat folds with a fillet of solder. Make sure the hole is still clear for the 8thou wire.

Folding primary spring seats Check that a 0.5mm drill will pass the holes in the primary spring seats (in the production etches they are holes rather than the open slots shown in these photos).

Invert the etch and fold the outer primary spring seats.

Flitch side plates folded up Invert the etch again and fold up the side plates.

Pony frame and flitching Offer up the Pony Frame (S7) to the Pony Flitching (S10).

Pony frame and flitching assembled Fit the two parts together, adjusting the folds as necessary.

Narrowing of mainframe outer ends Along the vertical fold lines, fold in the outer ends of the Mainframe (S4) a small amount.

Pony flitching and frame fitted to mainframe Adjust the folds so that they are equal and fit snugly against the sides of the Pony Flitching (S10) etch.

Pony frame and flitching in assembly jig Hold the components firmly together in alignment…

Pony frame and flitching top view …and solder them up both above…

Pony frame and flitching underside view …and below the flitch plate.

Pony Bearer etch Remove the Pony Bearer etch (S6) from the fret.

Bearer retaining ears folded Fold in the four spring retaining ears around the etch, and reinforce the folds with solder.

Folding bearer sides Fold up the two sides of the etch.

Fitting spring seat to Pony Bearer Pass a length of the 0.9mm wire through one of the holes in the side of the etch. Position it so that it reaches to a point approximately in line with, but no further than, the notch in the front edge of the etch, and solder it in place.

Trim the wire flush with the outer face of the side.

Completed Pony Bearer Repeat for the other side.

Pony Outer Frame etch Remove the Pony Outer Frame (S9) from the etch.

Check that the 8 thou spring wire will pass the hole in the etch. Drill it through 0.3mm if necessary.

Folding outer pony frame Fold up the two arms of the etch.

Mainframe inverted Support the Mainframe assembly inverted, with the top plate of the Pony Frame resting on a parallel surface.

Outer Pony Frame fitted. Slot the Outer Pony Frame into the Pony Frame.

Dressing edges of Pony Axle Dress the edges of the Pony Axle assembly with a file, to remove the etching cusps and any sharp edges.

Adjusting Outer Pony Frame to Pony Axle Drop the Pony Axle assembly into the slot formed by the Outer Pony Frame.

Adjust the position of the Outer Pony Frame to give a free sliding fit for the Pony Axle assembly in the slot. You might need to file a small amount from the interlocking slots or tags to achieve this.

The fit of the Pony Axle in the slot should provide free sliding radial and vertical movements for the axle and allow it to tilt a small amount (no more than to allow the wheel on one side to rise or fall about 0.5mm with respect to the wheel on the other side). There will be a little bit of 'play' in the location of the axle.

Outer Pony Frame ready for soldering Remove the Pony Axle assembly and solder the Outer Pony Frame in position.

Test the fit of the Pony Axle assembly. If necessary, make further adjustments to the Outer Pony Frame location until the desired fit is achieved.

Pony Bearer and Axle in place Remove the Pony Axle and test the fit of the Pony Bearer in the slot, dressing its edges with a file if necessary to give free vertical movement in the slot.

Inner Cross Member Remove the Inner Cross Member (S3) from the etch.

Inner Cross Member fitted Fit the Inner Cross Member to the halving joints at the inner end of the Mainframe, and solder them up. Use the slots closest to the end for the Class 40. For the Peak, use the other pair of slots, and cut and file away the projecting parts of the Mainframe.

Primary Splint Remove two of the Primary Splint (S11) etches from the fret.

Folding Primary Splint Make the 180° folds in the Primary Splints, with the half-etched folding tag on the inside of the fold.

Wire in Splint Cut two 40mm lengths of the primary spring (16thou) steel wire.

Apply flux to the inner faces of the splints, and close them on to the primary spring wires, with an equal length of wire protruding from each side. Apply a little grease to the central slot, to prevent solder from blocking it.

Completed inner primary springs Hold each splint firmly closed, with the spring wire caught in the longitudinal slot, and solder them up.

Clean up to ensure that there is no solder on the outer faces of the splints, and that the slots in the splints are clear of solder.

Completed Subframe assembly Clean up the Subframe assembly to remove any stray solder from its outer faces, including from the half-etched housings for the primary spring splints.

Check the assembly for squareness, and that the sides are vertical.

Reinforce the Mainframe folds, under each axle, with fillets of solder.